Different classes for different editor types

[krzywon]

Is your feature request related to a problem? Please describe.
Currently, the TabbedModelEditor class is used to edit py/c model files as well as rst documentation files. This is causing a number of branching logic elements that could be removed by subclassing.

Describe the solution you'd like
Make separate classes for the Doc editor and the Model editor, both would be child classes of a top-level TabbedEditor class.